1. Field of the Invention
The present invention is directed to a means for transporting a web-shaped recording medium in an electrographic printer or copier device.
2. Description of the Related Art
In printer devices of this species, the recording media are transported along a printing station and printed thereat. As needed, the recording medium is thereby composed of paper, of plastic film material or of other materials as well. The recording medium is printed over a specific width in the transfer printing station of such devices.
Dependent on the embodiment of the printer device, single sheets, roll goods with margin perforation or roll goods without margin perforation can be printed. Whereas paper with lateral holes for transport and position monitoring of the paper is employed in many applications, paper grades that exhibit no such margin perforation but are nonetheless fabricated as roll goods or fanfold paper are also increasingly employed.
Published International Patent Application WO 95/19929 A1 discloses a printer that can process roll paper without margin perforation as well as with margin perforation. A first seating edge, which prescribes the lateral position of the paper, as well as stabilization rollers, an under-pressure brake and a roller arrangement with a loop-drawing means are provided in this printer for the exact guidance.
Given printers of this type, there is often the problem that the paper transport unit must be disassembled for service purposes. For example, it regularly occurs that what is referred to as a corotron wire breaks during printing operation and a new corotron wire must be introduced. When such a service instance occurs during printing operation, then it is desirable to return the paper into the same position after the service action that it was in previously. Otherwise, a relatively complicated procedure must be started in order to restart the printing operation, whereby it is usually necessary to reprint various pages. Not only does excess printed matter (maculature) arise as a result thereof, additional outlay for sorting the reprinted paper out is also incurred.
European Patent document EP 0 399 287 A2 discloses a device for transporting a web-shaped recording medium in an electrographic printer or copier device. The carrier shaft and the drum for transporting the web-shaped material are arranged essentially coaxially.
German Patent document DE 42 14 126 A1 discloses an apparatus wherein a carrier is seated pivotable around a drum axis. The carrier is pivotable together with the drive drum and a contact pressure drum.
U.S. Pat. No. 4,642,661 discloses a transport mechanism for a web-shaped recording medium in a printer device, whereby transport and contact pressure elements of a pin feed wheel or, respectively, tractor drive are arranged at a carrier. The transport and contact pressure elements can be swivelled around an axis together with the carrier, whereby the drive shaft of the tractor proceeds concentrically relative to the swivelling axis of the carrier.
It is an object of the present invention to provide a means for transporting a web-shaped recording medium in an electrographic printer or copier device with which a positionally exact printing is also retained in the region of the transport unit after a service call.
This object is achieved by the apparatus described with the features of a carrier carrying a plurality of drive and guide elements, the carrier being pivotably seated at the housing of the printer or copier device via a carrier shaft and being capable of being pivoted back and forth between a working position and a service position; a drive drum seated at the carrier, the recording medium being transported by the drive drum with friction and the drum proceeding coaxially with the carrier shaft; contact pressure means with which the recording medium is pressed against a toner transfer means, particularly against a photoconductor drum, in the transfer printing area of the printer or copier device; and a means with which a retaining moment can be transmitted onto the recording medium during the pivot motion for stabilizing the position of the recording medium relative to the drive drum, and by the method for transporting a web shaped recording medium in an electrographic printer or copier device, including a carrier carrying a plurality of drive and guide elements is provided, the carrier being pivotably seated at the housing of the priner or copier device via a carrier shaft and being capable of being pivoted back and forth between a working position and a service psoition; a drive drum seated at the carrier is provided, the recording medium being transported by the drive drum with friction and the drum proceeding coaxially with the carrier shaft; contact pressure means with which the recording medium is pressed against a toner transfer means, particularly against a photoconductor drum, in the transfer printing area of the printer or copier device; are provided; and a retaining moment is transmitted onto the recording medium during the pivot motion for stabilizing the position of the recording medium relative to the drive drum. Advantageous exemplary embodiments of the invention provide a lock mechanism with which the means can be locked in a working position at the housing of the printer or copier device; and means for power support with which the means can be brought into a service position in the unlocked condition. In a preferred embodiment, the means for power support comprise a gas compression spring. The gas compression spring is rotatably seated at the carrier at a first bearing point and at a second bearing point at a bearing block that is rigidly connected to the device housing. The drive drum is driven by a stepping motor, whereby the stepping motor is under power for exerting the retaining moment while the means is being pivoted from a working position into a service position and back into the working position. In one embodiment, the stepping motor is mounted at the carrier. A first adjustable detent is provided at the bearing block for adjustment of the means relative to the device housing along a first direction and a second adjustable detent is provided for adjustment of the means relative to the device housing along a second direction. The drive drum may interact with counter-pressure rollers that press against the drive drum with an adjustable spring power. Preferably, the drive drum is seated on the carrier shaft.
Inventively, the means for transporting a web-shaped recording medium in an electrographic printer or copier device comprises a carrier, which is pivotably seated via a carrier shaft at the housing of the printer or copier device, as well as a drive drum with which the recording medium is transported by friction. The drive drum is rotatably seated at the carrier. Further, pressing means are provided with which the recording medium is pressed against a toner transfer means in the transfer printing area of the printer or copier device. The carrier shaft and the drive drum proceed coaxially. As a result thereof, the position of the drive and guide elements mounted at the unit is retained relative to the paper given a pivot motion of the means or, respectively, of the drive unit. It is particularly provided for this purpose that the drive drum is driven by a stepping motor, whereby the stepping motor is placed under power while the means is pivoted from a working position into a service position and back into the working position. As a result thereof, a retaining moment is transmitted onto the paper web, this stabilizing the relative paper position during the pivot motions.
In particular, the drive drum is seated in the carrier shaft around which the unit is pivotable. As a result thereof, an especially exact allocation between paper and drive drum is assured during the swivel motion.
What the invention also effects is that the paper transport can be pivoted back and forth between a working position and a service position such that the relative position of the paper in the working position practically does not change with respect to device-fixed units such as the transfer printing station.
At least one adjustable detent is provided at a bearing block of the means for adjusting the drive unit relative to the housing of the printer.